1. Field of the Invention
The present invention relates to a quality evaluation method and apparatus for non-bran rice, for evaluating the quality of non-bran rice products that are made by performing non-bran processing for polished rice after being hulled.
2. Description of the Related Art
So-called non-bran rice that can be cooked without being washed before cooking has been conventionally known. As for a production method of the non-bran rice, the method for removing rice bran powders and aleurone layer adhering to polished rice by hulling in the water, the method for adsorbing and removing the rice bran powders and aleurone layer adhering to polished rice with a cohesive substance, and the method for removing rice bran powders and aleurone layer by polishing polished rice with a dry method, are known. The non-bran rice produced by such processes is required to be conveniently cooked without before-cook washing, and also to have further added quality such as good taste and excellent storage properties. The turbidity when shaking and mixing the products immersed in water, whiteness of the products, water content, fatty acid content, water immersion broken grain rate of the products and the like are taken as the evaluation items so far in order to determine the quality of the products.
For example, as for the turbidity, the evaluation is carried out according to the method comprising the steps of putting non-bran rice sample of 20 g into an Erlenmeyer flask, closing it with a rubber stopper after water of 200 ml is poured, shaking it for ten minutes (144 to 150 cycles/minute, speed scale 3.5) with a shaking machine (made by Yamato Scientific Co., Ltd., Shaking machine, the model SA-31A), and measuring the diluted solution thereof with a turbidimeter (made by Nodal Communications Co., Ltd., Turbidimeter, the model M-204). It is generally considered desirable as non-bran rice if the measured value with the turbidimeter is 80 ppm or less.
However, with the above-described evaluation items such as turbidity, whiteness, water content, fatty acid content, and water immersion broken grain rate, the same evaluation items as used for the polished rice before non-bran rice processing are applied to the non-bran rice, and thus it is not possible to discriminate a test a layer, a Prichard layer and an aleurone layer, which constitute a very small amount of rice bran ingredients adhering to the surface of the non-bran rice to be a product, from an endosperm layer. Since the evaluation method of non-bran rice which makes it possible to identify a very small amount of rice bran ingredients is not established as described above, an evaluation and measuring apparatus exclusive for non-bran rice does not exist as an inevitable consequence. It is considered to perform point rating for each non-bran rice by means of taste evaluation apparatuses which are widely used in rice polishing factories and the like, but it is actually the point rating of the types and brands of polished rice and taste by sensory testing. Thus it is difficult to evaluate the quality of non-bran rice of which processing yield and surface condition are different from polished rice.
Incidentally, it is conventionally known that the compositions of protein and starch are identified by utilizing fluorescence emission. For example, U.S. Pat. No. 4,421,772 discloses a method which makes it possible to identify a hull layer, an aleurone layer, and starchy endosperm part of a grain with reliability. According to the method, it is characterized by including, in the method for identifying the component proportions in the grain product made by crushing, the step of irradiating electromagnetic radiation rays in the wavelength range of about 250 to about 300 nm to excite a starchy endosperm part in the product to emit fluorescence, irradiating electromagnetic radiation rays in the wavelength range of about 300 to about 370 nm to excite an aleurone layer part in the product to emit fluorescence, and further irradiating electromagnetic radiation rays in the wavelength range of about 410 to about 490 nm to excite a hull layer part in the product to emit fluorescence, and the step of analyzing the resultant fluorescence emitted by the product to identify the relative component proportions of the starchy endosperm, the aleurone layer and the hull layer in the product.
Meanwhile, U.S. Pat. No. 4,713,781 discloses a grain damage measuring system for identifying a damaged part and a part not damaged by illuminating a grain sample with a lamp of electromagnetic radiation in a selected wavelength range, causing the exposed starch part of the grain to fluoresce, and thereby causing visual contrast between the damaged part and the part not damaged of the grain sample.
However, the grain component identifying method disclosed in U.S. Pat. No. 4,421,772 is a technique of irradiating the starchy endosperm part, aleurone layer part and hull layer part with peculiar excitation wavelength suitable to the respective regions, and combining the fluorescence emissions separately measured into the entire grain, and therefore it has the disadvantage that the spot, where the area of the aleurone layer part and the area of the hull layer part overlap, occurs (excitation overlapping phenomenon), and accurate component analysis cannot be made.
In the grain damage measuring system disclosed in U.S. Pat. No. 4,713,781, it can be only determined whether or not the grain is damaged, and therefore this is not used for component analysis of a grain. Further, in both of the Patents, each of the ingredients of the grain is not related to a sensory value such as taste, while in the conventional taste evaluation apparatus, influence of a very small amount of rice bran adhering to the non-bran rice surface on taste is not considered, and thus detailed analysis of taste evaluation for non-bran rice cannot be made.